You didn't say from where you would be coming but???
If at all possible use I-80 ........ pretty much flat except for the climb out of Utah into Wyoming.......
or drop down to I-40....... I-70 is a heck of a climb but the scenery is much better than I-80 or I-40......
Best of luck either way..... have a safe trip.

i pull off my muffer off and put a cold air box on ,5.9 at 545 and i get 13 mpg for a 72 passger bus. that big air filler on the bus that came with it.it reduce the air flow,so rerout the air intake and put a dodge air filer on it for a cummins.

I cut mine off at the back wheels area just in front of the axels and face it down and i don't even here it,i use all the pipe i toke off. MY bus just had a new muffer put on befor i bought it,,so if anyone needs a new one,,here it sits

also the cold air box is just behine the bumper alone the frame... makes that tubo sing

Mine runs down pass frame,and then after the 4 foot muffler,it swoops in a big circle and passes over to the driverside (all that extra tubing just so kids didn't get smoked out when dropped off at the curb at school)

__________________Our build La TortugaAccept the challenges so that you can feel the exhilaration of victory. George S. Patton

Removing a muffler on a 5.9 is a good thing as the turbo reduces any loud exhaust. Consider leaving about 5-6 ft of exhaust under bus and install a 90 degree fitting to direct exhaust to the side of bus.
TC means torque converter which is the coupling between engine and transmission. The Allison MT643 has a lock up converter. The AT 454 cannot be retrofitted with a lock up converter. Consider changing the rear axle gears for better economy. For a bit more power, consider water/alcohol, LPG, or nitrous gas. Check lots at google. Frank
Remember advice is worth what is paid. Not all advice is good. Use lots of research to prove every bit of information.

In many cases, advice has a value equal to any payment. He said, she said, is bad information. Get a measuring device and go to a tire store and measure lots of tires with 22.5 and 24.5 wheel size. I think there is about just 1 inch difference. Rear gear change is the best for making better fuel economy. Frank